Rotary filter



APril 13, 1937 A. J. BARNEBL 2,076,611

ROTARY FILTER Filed June 27, 1935 2 Shee'ts-Sheet 1 April 13, 1937. A. J. BARNEBL 2,076,611

ROTARY FILTER i Filed June 27, 1955 2 Sheets-Sheet 2 muy, )fedex M Est Patented Apr. 13, 1937 PATENT OFFICE 010.011 BDTABY mm August I. Barncbl, Chicaglll., asignan-to Swenson Evaporator Campano. Harvey lll.. a comrationoflllinoh Application Juno 27. 1985, Serial No. 28,681 8 Claims. (Gl. 21o-201) This invention relates to rotary iilters, and particularlytorotaryflltersinwhichalayerofsolids is maintained upon the filtering surface. the filtrate passing through said solids and said surface. The invention is particularly applicable to rotary filters in which a layer of precoat is applied to the filtering surface and it will be specifically described in connection with the type of filter described and claimed in my copending ap- 10 plication Serial No. '745,201 illed September 24,

The aforesaid application discloses a rotary drum filter, the nltering surface being the cylindrical surface of the drum. In using this filter,

a substantial layer of precoat is built up upon the :Elltering surface and then the illtering operation is commenced. During the filtering operation the filtered solids and part of the precoat layer are removed continuously as the drum rotates, by

means of a knife. The iilter comprises means for feeding the knife progressively towards the filtering surface at a slow rate, so that the precoat is removed in the form of a thin convolution presenting a new and highly effective lterin surface to the filtered liquid at all times.

Difliculties have been encountered owing to the fact that there is a tendency for the knife to lift oi'f the precoat more than the desired thickness. In some cases the freshly shaved surface is found to be pitted. These pits may be considerably deeper than the thickness of precoat shaving removed, with the result that the surface of the pits becomes sealed by fine solids and other substances contained in the liquid to be iiltered. 'I'his sealing persists until the particular pits are eradicated by the progressive cuts of the knife, at which time other pits have been formed. The total result is that the capacity of the filter is substantially cut down, and the principal object of the 40 present invention is to provide means whereby the formation of such pits can be substantially avoided and the filtering capacity maintained during the operation of the filter.

The invention will readily be understood from the following description of a preferred embodiment thereof, taken in conjunction with the accompanying drawings, in which Figure 1 is a fragmentary end elevational view of a rotary lter embodying my invention;

Fig. 2 is a sectional detail view through the knife and adjacent portion of the filter drum and through the cake presser element, and

Fig. 3 is a fragmentary view showing these elements in front elevation.

Referring to the drawings, the reference nupivotally mountedon its axis and partly immersed in liquid to be nltered contained in a tank Il. The cylindrical surface of the drum may suitably comprise a perforated wall I2 over which is applied a ilne mesh screen i3 supporting and covered by a suitable fabric Il. as best shown in Fig. 2. 0n the inner side of the wall i2 are formed pockets Il, which communicate through pipes Il withthe hollow trunnion (not shown) of the drum il, through which suction or a vacuum is applied in known manner to draw liquid and air into the pockets Il. It will be understood that the drum l0 is rotated at a slow speed by any suitable or conventional mechanism (not shown).

I provide a knife I'I for shaving off the solid material which is to be separated from the liquid and also a small amount of precoat material. This knife is rigidly mounted on a strong transverse bar I8. which in turn is supported by means of depending arms IB from a horizontal bar 20. The horizontal bar 2li is rotatably mounted in bearings 2i carried by a stationary transverse member 22. 'I'he transverse member 22 is located above the tank Il so that the knife I1 operates on the lter surface above the level of the tank, as shown in Fig. l, and preferably on the downwardly moving side of the drum III. It will readily be seen from Fig. l that any material shaved ofi the drum IU by the knife I'I can fall clear of the tank Il.

At one end the bar 20 has rigidly secured thereto a lever 22 which extends downwardly towards the top of the tank Il and its lower end is provided with a bifurcated member 2l. The legs of the bifurcated member lie on each side of a nut 2l. Each leg of the member 24 is provided with an axial slot 28 which receives a trunnion 2l, these trunnions projecting laterally from the nut 25. The nut 25 is provided with a longitudinal keyway 28 which receives. with .a sliding fit. a key 28 formed on a base 30, the base being rigidly mounted on the upper edge of the tank Il.

The base 2B is provided with bearings 2| and l2 for a shaft 33. The bearing 3| is a doublethrust bearing and the shaft 33 is held against longitidinal movement by means of a shoulder 2l formed thereon, and a nut 3l threadedly mounted on the reduced and threaded portion of the shaft on the other side of the bearing Il from the shoulder Il.

At its outermost end the shaft 33 is provided with a manually operable wheel 26. wherebythe shaft 33 may be rotated by hand. The shaft 32 is provided with a relatively long threaded portion 31 which is adapted to cooperate with a relatively short threaded portion of the nut 2l.

At the other end. the nut 2l is provided with an internal sleeve or bushing 3l which receives the 5 unthreaded portion of the shaft Il with a free sliding fit.

A coil spring Il is located around the shaft 2l between the threaded portion 31 and the bearing l2. When the shaft Il is rotated from the filter during its operation, as will hereinafter be described. the nut 2l is moved progressively to the right as viewed in Fig. 1, until the threaded portion of the nut runs oil' the threaded portion 81 of the shaft ll. Before this occurs, the spring 8| comes into engagement with the nut 2l and prevents movement of the knife I1 into contact with the filter fabric Il of the drum Il. Purthermore. the spring II keeps the threaded portion of the nut 2l against the threaded portion I1 of the shaft, and when the shaft 3l is'rotated in the opposite direction. the nut 2l immediately screws on to the threaded portion l1.

On the other side of the bearing I2 from the spring I9, the shaft I8 has rigidly mounted thereon a clutch member Il. 'Ihis clutch member is adapted to he engaged by a complementary clutch member 4i slidably mounted on. and keyed to, a shaft 42 which is in alignment with the shaft Il. The clutch member ll can be slid into and out of engagement with the clutch member 40 by means of a forked hand lever 42 which is pivotally mounted upon the base or casting I0. This casting also provides a bearing Il for the shaft l2 and this shaft is connected by a suitable coupling 4l to the output shaft Il of a gear reduction unit Il. The input shaft 4l of the gear reduction unit I1 carries a sprocket wheel 4l which is driven by a chain lll. This chain passes over a sprocket (not 40 shown) mounted on the trunnion of the drum ill so that all the mechanism, 'including the knife, is operated continuously by the rotation of the drum. Because of the gear reduction unit 41.

which may have any suitable ratio, the shaft Il 45 and, when the clutch lever Il is in proper position, the shaft 33, may be made to rotate at the desired relatively slow speeds. Consequently, the nut 25 moves quite slowly and the knife I1 moves toward the filter fabric Il at a very 50 slow rate indeed.

Ordinarily, it is preferred that the movement of the knife l1 towards the filtering surface of the drum should not exceed 0.005" per revolution of the drum.

According to the present invention, 1' provide a cake presser element which is adapted to cooperate with the knife I1 and prevent the production of a surface having pits or depressions of any substantial size below the desired shaved 60 surface. In the embodiment illustrated, the

cake presser element is constituted by a bar of wood Il which extends transversely across the filter surface of the drum immediately above the knife I1. It is pivotally supported at each 65 end by means of pivot studs 82 which are rotatable in bearings BI carried by brackets Il which are rigidly mounted on the stationary transverse member 22. The presser element 5I is provided with a corner Il which is adapted to 70 bear against the filter cake slightly in front of the cutting edge of the knife I'l so as to apply pressure thereto. The pressure applied can be adjusted by means of weights IB which are adiustably mounted on rods l1 carried by the bar 75 li and projecting outwardly therefrom away from the filter drum. The weights IB can be secured in desired position on the rods l1 by means of thumb screws Il. It is preferred to locate the corner Il quite close to the edge of the knife I1. I prefer to have this corner about or V." ahead of the cutting edge in the circumferential direction of the drum. In this way the cake, including the filter cake and the precoat, immediately ahead of the knife. is maintained under pressure. It is my belief that the objectionable pitting and roughness of the shaved surface heretofore experienced has been due to the fact that the cutting effected by the knife has not been confined to the edge of the knife. 'I'here is a tendency for the filter cake to crake up ahead of the knife. Such cracking up is effectively prevented by the pressure applied by the presser element il, with the result that a much more perfect shaved surface is produced.

A typical operation of the filter will now be described. In this operation is employed a porous precoat formed from suitable precoat materials which are well known in the art and comprise foraminous or granular materials such as some clays, fuller's earth. diatomaceous earth and the like. The precoat used is applied as a layer upon the filtering siu'face before filtration is started.

One manner in which this may be accomplished ls to place a slurry of the precoat, that is, a suspension of precoat in water, into the tank II and start the filter drum revolving. At the same time vacuum is applied to the chambers I5, with the result that the liquid component of the slurry. usually water. is drawn through the fllter fabric I l and a layer of precoat is deposited on the surface of the fabric. This building up is continued until the desired depth of precoat, for example about 1" or 1%", is attained. Before the precoat is formed upon the lterlng surface of the filter drum, the knife I1 is backed up out of the way of the precoat. 'I'his is readily effected by throwing the clutch lever 4l into disengaged position and turning the shaft 38 by the hand wheel 36 so as to fit the nut 25 to the left, as viewed in Fig. l. This movement is continued until the nut 25 hits against the bearing ll, or at least until sufficient clearance has been provided for a precoat of desired depth.

After the precoat is formed, the tank Il may be drained and washed and then the material to be filtered is supplied thereto. The drum being in rotation and vacuum being applied to the chambers I5. the liquid component of the material being filtered is withdrawn through the precoat layer into the chambers Il, from which it passes in the usual way.

Aldeposit of solid material is now built on top of the precoat layer. 'I'he knife I1 is now advanced toward the filtering surface of the drum which may be eected by suitable rotation of the hand wheel It until the knife removes the coat of flltered material and preferably also a slight cut of precoat. Thereupon, the clutch lever l! is thrown into clutch-engaging position and thereafter the knife I1 feeds progressively towards the ltering surface of the drum so as to remove the filtered solids and also to remove a very slight cut, preferably less than 0.005". of precoat during each revolution.

If desired, the precoat layer may be trued by advancing the knife to the necessary depth by the hand wheel 4l, before the introduction of the material to be filtered.

As indicated above. the feeding of the knife I'l towards the filtering surface continues until the threaded portion of the nut 25 runs ofl' the thread 31 of the shaft 33, whereupon the spring 39 prevents the further advance of the knife I1 and the knife is automatically prevented from advancing far enough to contact the underlying fabric or drum. When this occurs, the nut 25 may be retracted by hand and a. new precoat layer built up.

It is preferred to drain the tank Il before the advance of the knife I1 terminates, and to shave the complete precoat surface before building up a new precoat layer thereon. This expedient enables me to avoid the presence of impervious or substantially impervious zones within the precoat layer.

Although the invention has been disclosed in connection with the speciiic details of a preferred embodiment thereof, it must be understood that such details are not intended to be limitative of the invention except in so far as set forth in the accompanying claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. A filter comprising a. rotary filtering surface, a knife adapted to shave material off said surface. means for maintaining said knife in spaced relation to said surface whereby only a part of said material is removed by the knife, and means for applying pressure on said material in the cutting position immediately in front of the cutting edge of the knife.

2. A fliter comprising a rotary filtering surface, adapted to receive a precoat of substantial thickness, a knife adapted to shave ltered solids and a thin layer of precoat on said surface. automatic means for feeding said knife slowly and progressively towards the filtering surface, and means for applying pressure on said material and precoat in the cutting position immediately in front of the cutting edge of the knife.

3. A filter comprising a rotary filtering surface. a knife adapted to shave material off said surface, and a pivotally supported bar applying pressure on said material at the shaving position.

4. A filter comprising a rotary filtering surface, a knife adapted to shave material oil said surface, means for maintaining said knife in spaced relation to said surface whereby only a part of said material is removed by the knife, and a pivotally supported bar applying pressure on said material immediately in front of the cutting edge of the knife.

5. A filter comprising a rotary filtering surface adapted to receive a precoat of substantial thickness, a knife adapted to shave filtered solids and a thin layer of precoat oii said surface, automatic means for feeding said knife slowly and progressively towards the filtering surface, and a pivotally supported bar applying pressure on said material immediately in front of the cutting edge of the knife.

AUGUST J. BARNEBL.

CERTIFICATE OF CORRECTION.

Patent No. 2,076,611.

April 13, 1937.

AUGUST J. BARNEBL.

It is hereby` certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page l, first column. after line 55. insert the syllable and worde meral 10 ndicates a filter drum of known type; and that the said Letters Patent Should be read with this correction therein that the same may conform to the reoord of the case n the Patent Office.

Signed and sealed this 1st day of June, A. D. 1937.

(Seal) iielnry Van Arsdale Acting Commissioner of Patents.

As indicated above. the feeding of the knife I'l towards the filtering surface continues until the threaded portion of the nut 25 runs ofl' the thread 31 of the shaft 33, whereupon the spring 39 prevents the further advance of the knife I1 and the knife is automatically prevented from advancing far enough to contact the underlying fabric or drum. When this occurs, the nut 25 may be retracted by hand and a. new precoat layer built up.

It is preferred to drain the tank Il before the advance of the knife I1 terminates, and to shave the complete precoat surface before building up a new precoat layer thereon. This expedient enables me to avoid the presence of impervious or substantially impervious zones within the precoat layer.

Although the invention has been disclosed in connection with the speciiic details of a preferred embodiment thereof, it must be understood that such details are not intended to be limitative of the invention except in so far as set forth in the accompanying claims.

Having thus described my invention, what I claim as new and desire to secure by Letters Patent of the United States is:

1. A filter comprising a. rotary filtering surface, a knife adapted to shave material off said surface. means for maintaining said knife in spaced relation to said surface whereby only a part of said material is removed by the knife, and means for applying pressure on said material in the cutting position immediately in front of the cutting edge of the knife.

2. A fliter comprising a rotary filtering surface, adapted to receive a precoat of substantial thickness, a knife adapted to shave ltered solids and a thin layer of precoat on said surface. automatic means for feeding said knife slowly and progressively towards the filtering surface, and means for applying pressure on said material and precoat in the cutting position immediately in front of the cutting edge of the knife.

3. A filter comprising a rotary filtering surface. a knife adapted to shave material off said surface, and a pivotally supported bar applying pressure on said material at the shaving position.

4. A filter comprising a rotary filtering surface, a knife adapted to shave material oil said surface, means for maintaining said knife in spaced relation to said surface whereby only a part of said material is removed by the knife, and a pivotally supported bar applying pressure on said material immediately in front of the cutting edge of the knife.

5. A filter comprising a rotary filtering surface adapted to receive a precoat of substantial thickness, a knife adapted to shave filtered solids and a thin layer of precoat oii said surface, automatic means for feeding said knife slowly and progressively towards the filtering surface, and a pivotally supported bar applying pressure on said material immediately in front of the cutting edge of the knife.

AUGUST J. BARNEBL.

CERTIFICATE OF CORRECTION.

Patent No. 2,076,611.

April 13, 1937.

AUGUST J. BARNEBL.

It is hereby` certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page l, first column. after line 55. insert the syllable and worde meral 10 ndicates a filter drum of known type; and that the said Letters Patent Should be read with this correction therein that the same may conform to the reoord of the case n the Patent Office.

Signed and sealed this 1st day of June, A. D. 1937.

(Seal) iielnry Van Arsdale Acting Commissioner of Patents. 

